1. Field of the Invention
The present invention relates to magnetic drive systems for generating linear movements, and in particular to such magnetic drive systems for use in operating a printing element of a high speed printer.
2. Description of the Prior Art
A magnetic drive system for a printing element of a high speed printer is disclosed in German OS No. 2,939,829 having an armature seated in a yoke for longitudinal movement relative thereto and at least one permanent magnet disposed in the magnetic circuit formed of the yoke and armature such that the magnet effects a magnetic flux in the armature which is directed from both ends of the armature to the center of the armature or vice versa. The yoke and armature consist primarily of material having a low magnetic retention. The yoke in this known system completely surrounds the armature and the magnets in the yoke are magnetized in the radial direction. Coils are disposed at both sides of the yoke for excitation in order to induce a flux which is superimposed on the flux generated by the permanent magnets such that the flux at one end of the yoke is amplified and is reduced at the opposite end. A force influencing the armature thus results which places the armature in motion in the longitudinal direction toward one of the coils. The magnetic forces resulting from the coil acting on the armature increase with increased movement of the armature. In addition to forces which ideally move the armature in the longitudinal direction relative to the yoke, considerable forces also act on the armature in the radial direction if the armature is not precisely centered in the yoke.
Because of the necessity to eliminate forces acting on the armature other than those forces which move the armature in a longitudinal direction, such conventional devices require that relatively expensive and time-consuming steps and structural outlay be utilized to precisely seat the armature in the yoke, therey adding to the overall cost of the drive system.